Studies will continue on the primary structure of human transferrin. The nine cyanogen bromide fragments that have been isolated will be further subjected to digestion with enzymes (trypsin, chymotrypsin, and thermolysin). Sequences will be established for those peptides not already sequenced. It is hoped that sufficient overlapping sequences will be obtained using the above methods so that the unique sequence for the entire molecule can be derived. Preliminary studies of sequences of other vertebrate transferrins, especially primates, will continue. Studies will also be carried out on somatic mutation in human red cells. The system to be investigated will be the mutation to persistent fetal hemoglobin. Both genetical and immunological methods will be used to identify variant red cells.